The director of Russia's biggest Pacific Ocean port has been shot dead in what's believed to have been a contract killing.

Officials said gunmen fired from two parked cars at Leonid Bochkov, the director-general of port facilites at Nakhodka, near Vladivostok in the Russian Far East. He died later in hospital.

Police said they made four arrests after a chase near the scene.

Investigators say they believe the attack may have been part of an attempt by organised criminal gangs to establish control over the Nakhodka port, which handles more than 13 million tonnes of cargo each year.

Twenty per cent of the port ownership was sold earlier this year to the Russian metal-making company Severstal, and local media suggested this may have sparked what they called a management conflict.